Require ScriptInstance to be valid in the editor debugger
Require ScriptInstance to be valid in the editor debugger

This fixes an issue with visual scripts spamming error messages
in the editor when running the project with the remote scene tree
visible.

(cherry picked from commit 829c8247559a21d0b6f540e4a548d935c3a24643)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot